An automatic analyzer capable of automatically exchanging reagents during analyzing has been known (see PTL 1, for example). The automatic analyzer disclosed in PTL 1 includes a reagent disc mechanism (reagent container storage portion) having a driving disc and a fixed disc which is arranged to be concentrically fixed with respect to the driving disc, a loading system (reagent loader) which forms a part of the periphery of the fixed disc and has a reagent placing unit capable of placing a plurality of reagent containers, and a reagent container moving unit which moves the reagent containers between the loading system and a reagent driving disc.